This invention generally relates to the field of cardiac valve replacement, and more particularly to a method of implanting a stentless valve prosthesis in an atrio-ventricular valve of a patient's heart.
A human heart includes two atrio-ventricular valves, namely the tricuspid valve between the right atrium and ventricle, and the mitral or bicuspid valve between the left atrium and ventricle. The atrio-ventricular valves are one-way valves, permitting blood flow from the atrium to the ventricle. During the cardiac cycle, the valves function as part of a unit composed of multiple interrelated parts, including the ventricular and atrial walls, the valve leaflets, the fibrous skeleton of the heart at the atrio-ventricular ring, and the subvalvular apparatus. The subvalvular apparatus includes the papillary muscle within the ventricle, and the chordae tendineae which connect the papillary muscle to the valve leaflets.
Surgical procedures for repairing or replacing diseased atrio-ventricular valves are well known. Reparative techniques are typically not feasible in cases involving extensive fibrosis, leaflet calcification, or massive chordal rupture, leaving valve replacement as the only surgical option. The valve may be replaced either with a mechanical or biological valve prosthesis. Biological valve prostheses are formed of tissue, and include allografts, e.g., aortic valves from cadavers, and xenografts formed of animal tissue. The valves may include a metal or plastic support, typically called a stent, or may be stentless.
Mitral valve replacement generally involves either conventional replacement methods or chordal-sparing replacement methods, as described in K. L. Yun et al., Mitral Valve Replacement, Chpt. 2, Adult Cardiac Surgery, in Mastery of Cardiothoracic Surgery, L. R. Kaiser et al Eds., 329-341 (1988), incorporated herein by reference in its entirety. In conventional replacement, the mitral leaflets and subvalvular apparatus are completely removed before the prosthesis is implanted. In contrast, in chordal-sparing replacement, at least the choral attachments to the posterior leaflet of the mitral valve are preserved. Maintaining the continuity of the mitral annulus and papillary muscle by preserving the subvalvular apparatus during mitral valve replacement has been suggested as an important feature in maintaining normal left ventricular function, as described by Lillehei et al, J. Thoracic and Cardiovas. Surg., Vol. 47, No. 4, 532-543 (1964), incorporated herein by reference in its entirety. Following implantation of a stented valve prosthesis, one difficulty has been reduced heart function, including limitation of the mitral flow, higher cardiac output due to a size mismatch between the prosthesis and native valve, and limitation of the physiologic contraction of the posterior wall of the left ventricle surrounding the mitral annulus during systole due to the rigid structure of some valve prostheses.
It would be a significant advance to provide a method of implanting a stentless valve prosthesis in an atrio-ventricular valve which maintains normal heart function.